...

You can add a comment by clicking on any element on the board and selecting the comment icon from the menu above it. 

Image RemovedImage Added

If you open the context menu by clicking the ellipsis at the end of the menu, you can also leave a comment from there. 

Image RemovedImage Added

Another way to leave a comment is to enable the comment mode by clicking the comment icon on the left-hand toolbar. Once turned on, click any element on the board to add a comment. 

...

• Comments you’ve already seen or thatwere left by you have a yellow icon.
  Image RemovedImage Added

• New comments or comments with new replies get a red dot next to the comment icon. Whenever there’s a new reply or comment, you will also see a red dot added to the comment panel icon on the right-hand toolbar.
  

• Comments where you are mentioned get a red dot with a number corresponding to the number of times you’ve been mentioned. You will also see the number of your new mentions on all comments on the board on the right-hand toolbar.
  Image RemovedImage Added

• Resolved comments have a check mark inside the comment icon. 
  
  

...